My vet told me to use any probiotics made specifically for birds. So I went to Amazon, typed in, "avian probiotics," and alternate between two I found there.
PetAg Bene-Bac https://www.amazon.com/dp/B0002DGYIC/ref=cm_sw_r_cp_api_i_cP1DFbS23NMV2
HealthyGut Avian Probiotics...